In a medium bowl, mix together the oats and buttermilk. Cover, and refrigerate overnight. The next morning: In a large bowl, sift together the flour, sugar, baking powder, baking soda, cinnamon, and salt. Make a well in the center, and pour in the oatmeal mixture, eggs, butter, and raisins. Stir until just moistened. Allow batter to sit 20 minutes before cooking. If batter is too thick, add buttermilk 1 tablespoon at a time, until the batter reaches the desired consistency. Heat a lightly greased, large skillet or griddle over medium heat. Pour 1/4 cup batter onto the hot griddle for each cake. Cook pancakes until bubbles appear on top, flip, and cook until lightly browned on bottom.